\\[-1.8ex] Soil Heterogeneity & $-$0.248$^{*}$ & $-$0.240 & $-$0.244$^{*}$ \\ 
  & (0.148) & (0.170) & (0.143) \\ 
\\[-1.8ex] 
Observations & 21,657 & 20,584 & 20,397 \\ 
R$^{2}$ & 0.644 & 0.645 & 0.674 \\ 
